Timing relay

ABSTRACT

A timing relay is driven by an electronically-controlled variable-speed D.C. motor so that the speed is adjusted to correspond to the time interval selected; the timing indicator gives a full-scale deflection for all time intervals and the increment of timing error is constant irrespective of the time interval used.

United States Patent Schleicher [451 Nov. 12, 1974 TIMING RELAY Inventor: Helmut Schleicher, Berlin, Germany Filed: Nov. 12, 1970 Appl. No.: 88,941

Foreign Application Priority Data Nov. 12. 1969 Germany l9579ll U.S. Cl. 317/141 R, 200/38 D Int. Cl. H01h 47/18 Field of Search 200/38 D; 307/l4l.4;

References Cited UNlTED STATES PATENTS Lowkruntz 3l7/l4l R Primary Examiner-L. T. Hix Attorney, Agent, or Firm-Paul M. Denk [57] ABSTRACT A timing relay is driven by an electronically-controlled variable-speed DC. motor so that the speed is adjusted to correspond to the time interval selected; the timing indicator gives a full-scale deflection for all time intervals and the increment of timing error is constant irrespective of the time interval used.

3 Claims, 1 Drawing Figure TIMING RELAY This invention relates to a timing relay, in which an optionally preselectible time interval may be set within predetermined limits by means of an adjusting knob.

Conventional timing relays are normally actuated by means of a coil equipped with a displaceable yoke. The displaceable yoke is held away from the iron core in the non-energised state by spring force, and is attracted to the iron core when the relay is energised and thereby moves a release level fast with the yoke, which is pivotable through a small angle, said release lever in turn releasing a locking pawl, a pinion being engageable in a time sequence wheel against a spring force by means of the locking pawl. The motor of the relay, which produces the time sequence and which drives the pinion engageable in the time sequence wheel through gearing, is energised at the same time as the coil. The timing sequence of the relay thus begins immediately with the action engaging the pinion in the time sequence wheel, the latter being so arranged that it may optionally actuate one or more switching contactors. In the known timing relays, the time sequence wheel carries a pin and simultaneously with its rotary displacement, tensions a a return spring one end of which is secured to the time sequence wheel. The time sequence wheel is connected by a spindle to a pointer accessibly arranged on the front plate or dial of the relay, which runs against a preset timing mark, during the sequence. Depending on the period set on the scale, the pin secured on the time sequence wheel describes an angle of rotation of corresponding magnitude and after traversal of this angle releases a locking pawl which in turn, directly or indirectly actuates the contacts set for operation after a preselected delay. After this, the time sequence wheel is snapped back to its idle position by the action of the return spring.

Such timing relays are operated by synchronous motors which being energisable solely by means of alternating current run at an invariable speed of revolution.

A timing error arises during the action, described above, of coupling the pinion of the transmission connected to the motor with the time sequence wheel, because both the teeth of the pinion and those of the time sequence wheel, do not always engage instantly but can slip before they fully intermesh. This error due to slip leads to an inaccuracy of the setting of the entire time sequence and occurs again with each fresh switching action; it is always of the same magnitude, irrespective of the time set.

The manufacturers of timing relays accordingly specify a margin of error for the adjustable time intervals, this margin depending on the different manufactures amounting to 0.5 percent as a mean, measured over a full scale deflection. In the case of adjustable time values which are smaller than a full scale deflection and particularly for those which are situated in the lower area of the scale, the coupling error which is intrinsically a constant plays a more significant part. A timing error specified as 0.5 percent for the full scale thus amounts to 5 percent for a preset period of one-tenth of the full scale deflection for example, even amounting to percent for one-twentieth of the total scale value, etc. Depending on the individual scale values, the timing error does not intervene linearly in the setting but exponentially, the timing inaccuracies playing a partieularly significant part in the case of short time settings.

The present invention aims at providing a timing relay wherein a minimum timing error remains constant irrespective of the time interval to be established. i.e., which as a function of time no longer intervenes exponentially as in the conventional timing rclays, but linearly.

According to the invention, the solution of the problem is broadly based on the fact that the motor which determines the timing sequence and actuates one or more switching contacts by means of a time sequence wheel equipped with a return spring, corresponding locking pawls and release levers, is a known type of direct current motor the speed of revolution of which can be varied by means of a potentiometer acting through an electronic circuit.

In this connection, it is of essential significance that, according to the invention, the speed of revolution of the direct current motor is adjustable by means of the adjusting knob of the potentiometer and a scale cooperating therewith and calibrated accordingly in time intervals, in such manner that the pointer indicating the preselected time sequence traverses the entire scale range in each case.

It is also advantageous for the direct current motor employing electronically controlled speed control to be provided with a rectifier, so that the timing relay can be operated either from direct or alternating current.

In a preferred example of embodiment of the invention, it is essential moreover that the output pinion of the direct current motor is connected through variable gearing which may be coupled in series, depending on the time scale subdivision required.

The solution provided by the relay of the present invention accordingly no longer consists in that the timing period is produced by means of a pointer coupled to the time sequence wheel as hitherto, but in contra distinction to the operation of known timing relays, by appropriate preselection of the speed of revolution of the motor operating the timing relay.

It would also be possible in principle to obtain continual changes in speed of revolution even with conventional d.c. collector motors. Depending on the voltage applied, the rotor of the dc. collector motor may also be operated at different speeds of revolution. These conventional d.c. motors are not suitable however in view of the stringent requirements for timing relays. On the one hand, these motors have a relatively large socalled cold-hot error which considerably impairs the accuracy of the preselected period, on the other hand, they require an amount of maintenance which is unacceptable for modern timing relays. Conventional d.c. motors are equipped with commutators in contact with carbons or brushes which are subject to considerable wear. As a result, the commutator brushes must be replaced from time to time. The springs pressing the commutator brushes against the commutator undergo fatigue, thus resulting in arcing and finally in inadequate contact.

By contrast, an essential advantage of the direct current motor incorporated in the timing relay of the present invention and employing electronically operated speed control, resides in that it operates without a commutator and thus without maintenance. Like a synchronous motor, the dc. motor employing electronically operated speed control is hardly liable to fail and has the additional advantage that it may be operated at will with alternating as well as direct current by employing an appropriate rectifier;

The appropriate preslection of the speed of revolution of the motor employed according to the invention, which can be adjusted in infinitely variable manner by means of a potentiometer, renders it possible to obtain a full scale deflection of the pointer for any optional time setting, i.e., to allow the time sequence wheel of the timing relay to run through the full deflection in the coupled state, irrespective of the time interval preselected. The coupling error induced by the coupling action thus remains constant for any optional choice of period, and especially for the shortest periods i.e. the error intervenes linearly as a function of time.

Owing to the fact that the pointer always gives a full scale deflection on the indicator scale, it is possible moreover for the operating personnel to make a positive check, inasmuch as the full scale deflection can be seen clearly thus enabling an energised relay to be distinguished from one in the idle state.

In order more clearly to understand the nature of the invention, reference is made to the accompanying drawing, which illustrates diagrammatically and by way of example, one embodiment thereof.

In the drawing, the relay according to the invention has a potentiometer 5 which can be adjusted by means of a spindle 4 and an adjusting knob 2 which is fast on this spindle. The pointer 3 of the adjusting knob 2 runs over a scale 1 which is calibrated according to the preselectible time sequence. Through an electronic circuit 6, a corresponding difference in potential is thus applied to the dc. motor 7 employing electronically operated speed control, by preselection on the potentiometer. The output pinion of the dc. motor 7 drives a variable gear system 8 the output-side pinion 12 of which may in turn be coupled or brought into engagement with the time sequence wheel by means of a locking pawl 15 and another release lever 16. The time elapsed is indicated by a pointer 14 which is arranged on an indicator scale 13 on the front plate of the relay. As in conventional timing relays, the time sequence wheel is connected to a return spring 11 which, after the switching operation has been performed and after its disengagement from the pinion of the variable gear system 8, ensures a rapid return to the idle position. The transmission is equipped with a step switching system in known manner so that different periods can be set by means of an adjusting or setting knob 9. In the embodiment described, the periods amount to 6 secs., 60 secs, 6 mins., 6 hrs. Within each time range, and as described above, an optional intermediate value may be set continually through the adjusting knob 2 and the potentiometer 5, and thus exclusively by appropriate preselection of a corresponding speed of revolution of the electronic d.c. motor.

The dc. motor with electronically operated speed control employed according to the invention for the timing relay described has no commutator, and has a stationary commutation system comprising semiconductors with control as a function of angular displacement for two Hall generators situated in the working airgap and displaced through 90 relative to each other. A typical example of such a motor, has four windings which are situated in the airgap of the motor and which are electrically interconnected at one point.

Of these armature windings, two are arranged coaxially relative to each other in each case. The interconnected ends of the armature windings lead to transistors which can be driven in pairs as a function of angle of rotation by one of the Hall generators in each case, each Hall generator controlling 'two transistors operating in push-pull. To this end, the control depends on the position of the rotor, in such manner that the transistors are placed in the open or closed state according to the direction of the rotor flux, two windings thereby being energised with current at any time. The current flowing through the armature windings likewise suffers a phase displacement by virtue of the given spatial arrangement of the Hall generators which are mutually displaced through 90. The two circulation vectors, result in fluxes the geometrical addition of which produces a circular field of rotation which, together with the rotor fiux, generates a torque.

The d e. motor employing electronically operate d speed control and employed according to the invention in a timing relay, may be so arranged on the one hand for the timing sequence of the relay that it begins to run upon energisation of the switching magnet, or with appropriate switching means, it may be employed as a continuously running motor which transmits its drive through the output pinion of the variable gear system 8 by coupling to the time sequence wheel 10, only during the preselected period.

For speed control of the dc. motor, a part of the EMF is compared with the constant base-emitter threshold potential of a reference transistor. The required speed of revolution is obtained by appropriate adjustment by means of the potentiometer 5. To this end, the voltage is proportional to the control voltage of the Hall generators and thus at the same time to the base and collector current of the power transistors which are arranged in the winding circuit.

The aforesaid selection in steps of different periods by means of the setting knob 9 may be enlarged if one or more gear systems allowing of further spread of the periods is or are co-ordinated with the multigear 8 connected to the output side of the dc. motor.

I claim:

ll. In a timing relay designed for minimizing error in the operation of said relay comprising, a timing relay, a direct current motor coupled to said relay to provide for its actuation, a potentiometer electrically connected to said motor to control its speed of revolution,

said relay incorporating time setting means to provide for adjustment in a timed opeation, and adjusting means connecting to said potentiometer and which is capable of being set to regulate the speed of said motor in relation to the timing period set for operation of said relay.

2. The invention of claim 5 wherein both said setting means and adjusting means are calibrated for faciitating their cooperative settings, whereby upon the predetermined related setting of each means, a longer delay in the actuation of said relay provides for a slower speed of revolution of said direct current motor.

3. The invention of claim 1 and further including a rectifier electrically connecting to said motor wherein rectified alternating current regulated by said potentiometer provides for energization of said direct current motor.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,8 l-8,163 Dated November 1 l97 L lnventofls) Helmut Schleicher It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 2, line 55, change "5" to 1 line 56,

change "faciitating" to facilitating Signed and sealed this 22nd day of April 1975.

(SEAL) Attest C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks FORM PO-IOSO (10-69) USCOMNPDC 60376.1:59 u.s. covznumzrrr PRINTING omcz: 930

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,8 +8,163 Dated November- 1h, 197

lnventofls) Helmut Schleicher It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 2, line 55, change "5" to 1 line 56,

change "faciitating" to facilitating Signed and sealed this 22nd day of April 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks FORM PC4050 (10-69) T uscoMM-Dc 60376-P59 u.s. GOVERNMENT PRINTING OFFICE: 930 

1. In a timing relay designed for minimizing error in the operation of said relay comprising, a timing relay, a direct current motor coupled to said relay to provide for its actuation, a potentiometer electrically connected to said motor to control its speed of revolution, said relay incorporating time setting means to provide for adjustment in a timed opeation, and adjusting means connecting to said potentiometer and which is capable of being set to regulate the speed of said motor in relation to the timing period set for operation of said relay.
 2. The invention of claim 5 wherein both said setting means and adjusting means are calibrated for faciitating their cooperative settings, whereby upon the predetermined related setting of each means, a longer delay in the actuation of said relay provides for a slower speed of revolution of said direct current motor.
 3. The invention of claim 1 and further including a rectifier electrically connecting to said motor wherein rectified alternating current regulated by said potentiometer provides for energization of said direct current motor. 